Re: [Qemu-devel] Drop support for 32bit hosts in qemu? (was: [PULL 1/6] audio/hda: create millisecond timers that handle IO)

[Alex Bennée]

Alex Bennée <address@hidden> writes:

> Dr. David Alan Gilbert <address@hidden> writes:
>
>> * Peter Maydell (address@hidden) wrote:
>>> On 27 June 2018 at 09:52, Gerd Hoffmann <address@hidden> wrote:
>>> >   Hi,
>>> >
>>> >> > Is QEMU still useful on 32-bit hosts?  Honest question!
>>> >>
>>> >> I guess it depends on what 32-bit hosts you consider. If you look at only
>>> >> x86 vs. x86_64 then probably x86 is not that important any more but for 
>>> >> some
>>> >> embedded systems/SoCs 32bit might still be common and QEMU useful for 
>>> >> those
>>> >> (also as host not only emulated).
>>>
>>> I would generally agree with this. For x86 32-bit is probably
>>> droppable, but for non-x86 the situation is much less clear.
>>>
>>> > Well.  I've used kvm with an 32bit arm soc (cubietruck).  It's very
>>> > slow.  And all the arm architecture improvements to support kvm better
>>> > are for aarch64 only.
>>>
>>> Cubietruck (a Cortex-A7) is a pretty slow 32-bit Arm core.
>>>
>>> Ask again in a couple of years :-)
>>
>> How about dropping support for 32 bit hosts that don't have
>> 64bit atomics?
>> That should be a much smaller set.
>
> Seems a bit harsh - we don't support MTTCG if you don't have big enough
> atomics, but we don't drop TCG support completely. And in fact in the
> case in point I don't think you could trigger a bug with emulation being
> single threaded and all.

I should point out that is what TCG_OVERSIZED_GUEST is defined for.

--
Alex Bennée